Tailoring hot‐exciton emitter via an accelerated reverse intersystem crossing process for deep‐blue organic light‐emitting diodes with an external quantum efficiency approaching 16% at 1000 cd m −2 and a CIE y of 0.027

Achieving high‐efficiency, saturated‐color, and stable deep‐blue organic light‐emitting diodes (OLEDs) is essential for ultrahigh‐definition displays; however, it still faces challenges due to the intrinsic wide band gap of emitters. Here, we report a deep‐blue hot‐exciton materials, 2TPA‐SAF‐CN , exhibiting typical hybridized local‐excited and charge‐transfer characteristics. By dividing 2TPA‐SAF‐CN into two fragments (short‐axis and long‐axis), it is found that the long‐axis enables 2TPA‐SAF‐CN deep‐blue emission and a high photoluminescence quantum yield of 93.2%, while the short‐axis accelerates the high‐lying reverse intersystem crossing process to a rate of 4.40 × 10 9 s −1 and improves the exciton utilization efficiency of 2TPA‐SAF‐CN by over 10%. As a result, a series of OLEDs based on 2TPA‐SAF‐CN is prepared, achieving a small CIE y coordinate of 0.027 with a high external quantum efficiency of 15.7% and negligible efficiency roll‐off at 1000 cd m −2 . The sensitized OLED of 2TPA‐SAF‐CN exhibits intense deep‐blue emission peaking at 452 nm with a half‐width of 22 nm and CIE y coordinate (0.048) close to BT.2020 standard, corresponding to an LT 85 of ≈626 h at an initial luminance of 100 cd m −2 . To the best of our knowledge, it is the leading performance of deep‐blue fluorescent OLED.